gw/nitrace is a SAP Parameter attribute which is used to control enable/disable tracing for network layer (NI) information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
Activates or deactivates the tracing of inbound and outbound network
0 = Trace is deactivated
1 = Trace is activated
See SAP Parameter Documentation for full SAP documentation for this profile parameter.